In a typical cellular communication network, a set of geographically dispersed base stations provide wireless access to a communications infrastructure. Users with wireless communication devices, or terminals, are able to establish a direct communication link with a suitable base station and then exchange information with other users and/or end systems throughout the communication network. In general, such systems could support a variety of different applications (e.g., telephony, text messaging, streaming audio/video, web browsing, file transfer, etc.); however, traditional systems have been primarily designed for telephony. The information exchanged over the access link includes user data as well as control signaling to support the access link itself, coordinate transmissions, enable mobility, and provide many other such features.
Typically, users of a cellular communication system are not continuously engaged in active information exchange (e.g., there may be significant periods during which the end user is not participating in a communication session). A location tracking and paging system allows the wireless terminal, during periods of inactivity, to transition into a dormant mode to reduce power consumption and maximize operational lifetime, while still maintaining inbound reachability. While operating in a dormant mode, a wireless terminal may still periodically monitor a special paging channel to enable the establishment of incoming communication sessions. Thus, the user of the wireless terminal may still receive calls. However, page signaling to alert a dormant wireless terminal of an incoming communication session is typically limited to a location area (or paging area) comprising a subset of base stations in geographic proximity to where the wireless terminal transitioned into the dormant mode or last reported its location. Thus, as a dormant wireless terminal migrates (e.g., changes cells or location/paging areas), additional control signaling is often used to update the location information (e.g., location/paging area) associated with the dormant wireless terminal. Depending on the system design, location update signaling may be performed periodically and/or upon certain events such as crossing cell or location/paging area boundary.
There is an engineering tradeoff regarding the accuracy of location tracking information. Maintaining accurate location tracking information requires more frequent location update signaling, thus increasing communication overhead and wireless terminal power consumption while in a dormant mode. Alternatively, with less accurate location information, page signaling may need to extend throughout a larger subset of base stations, thus increasing communication overhead associated with returning the wireless terminal to an active mode. Furthermore, depending on the paging strategy, less accurate location information also typically results in an increase in paging latency.
Traditional, circuit-switched, cellular networks designed primarily for voice telephony often employ relatively large location/paging areas consisting of tens or even hundreds of base stations. In such systems, dormant wireless terminals are free to move around the corresponding geographical area without being required to send location update signaling. The disadvantage of this approach is that when a dormant wireless terminal needs to be paged, many and possibly all of the base stations in the location/paging area participate in signaling the wireless terminal.
Circuit-switched, cellular network technology is presently being extended to support data applications. Additionally, there are emerging packet-switched cellular network technologies, which are better suited for supporting a wide range of applications, including interactive data applications like instant messaging and online gaming. A wireless terminal that supports a wider range of applications, particularly more interactive and transactional applications, is likely to more frequently transition between active and dormant modes; thus, there will likely be a significant increase in the frequency of paging attempts. This suggests the benefit of supporting smaller location/paging areas, which, as detailed above, may in turn require frequent location update signaling. Thus, there is a need for lightweight location update and paging mechanisms to enable a reduction in location/paging area size without overly increasing communication overhead or increasing power consumption (reducing operational lifetime).
In view of the above discussion, it is apparent that there is a need for improved methods and apparatus for location tracking and paging.